Energy drinks have been banned from Greymouth High amid growing concern over the number of girls skipping meals.
Health officials say many students have been substituting a proper breakfast with energy drinks, or not having breakfast at all.
A meeting will be held next week to discuss solutions.
The school has decided to ban energy drinks from the beginning of term two, starting on April 23. Students caught with them will have them confiscated.
Another school in the town, John Paul II High, has not banned the drinks, but says it does not sell them at the canteen or promote their consumption.